Detailed Description

bits 63-32 (BRLAPI_KEY_FLAGS_MASK), flags: bits 39-32 are standard X modifiers (shift, control, meta, ...). Other flags are used for some commands, see documentation of BRLAPI_KEY_FLG_* for their respective uses.

bits 28-0 (BRLAPI_KEY_CODE_MASK), key code: for braille commands, see BRLAPI_KEY_CMD_* ; for standard X keysyms, this is the keysym value, see X11 documentation, a complete list is probably available on your system in /usr/include/X11/keysymdef.h

The third part is itself split into two parts: a command number and a command value. The relative sizes of these parts vary according to the key type.

For a X keysym, if it is a unicode keysym (0x1uvwxyz), then the command number part is 0x1000000 and the value part is 0xuvwxyz. Else, the command part is held by bits 28-8 and the value part is held by bits 7-0. This permits to easily handle usual cases like 0x00xy (latin1), 0x01xy (latin2), XK_Backspace (0xff08, backspace), XK_Tab (0xff09, tab), ...

(key & BRLAPI_KEY_CMD_ARG_MASK) == 8, so the highlighted cell is the 9th one (cells are numbered from 0)

(key & BRLAPI_KEY_FLAGS_MASK) == 0, so no modifier key was pressed during the command, and no particular flag applies to the command.

if key == 0x000000010000FF09,

(key & BRLAPI_KEY_TYPE_MASK) == BRLAPI_KEY_TYPE_SYM, so it's a keysym

(key & BRLAPI_KEY_CODE_MASK) == XK_Tab, so it's the tab key. BRLAPI_KEY_SYM_TAB can also be used here, as well as a few other BRLAPI_KEY_SYM_* constants which are provided to avoid having to include X11/keysymdef.h

(key & BRLAPI_KEY_FLAGS_MASK) == BRLAPI_KEY_FLG_SHIFT, so the shift modifier was pressed during the command.

in the X11 standard some keysyms are directly unicode, for instance if key == 0x0000000001001EA0,